# What is Crystal systems ?

If you are searching about crystal system then you are on the right place . Here i am sharing with you about crystal system.To represent the type of distribution of network points in space, seven different coordinate systems are required.These coordinate systems are known as crystal systems.

There are total seven crystal system are (1) Cubic (2) Tetragonal (3) Orthorhombic (4) Monoclinic (5) Triclinic (6) Rhombohedral (or Trigonal) and (7) Hexagonal . Crystal systems are named on the basis of geometrical shape and symmetry. In 1948, Bravais described 14 lattices are sufficient to describe all crystals.These 14 lattices are known as Bravais lattices and are classified into 7 crystal systems on the basis of cell parameters.

## Seven Crystal Systems and Bravais Lattices

Seven crystal system and Bravais lattices are described below

#### 1. Cubic crystal system :

In this crystal system, the length of the unit cell edge is equal and at right angles to each other.for example a = b = c and α = β = γ = 90°.In simple cube lattice, lattice points or atoms are present at the corners of the cube. In a body-centered cube, atoms are present in the corners and an atom is completely present in the center of the cube. In the case of a face-centered cube, the atoms are present in the corners and in the center of all the faces of the cube.

#### 2. Tetragonal crystal system:

In this crystal system, two lengths of unit cell edges are equal while the third length is different. Three edges perpendicular to each other. for example a = b ≠ c and α = β = γ = 90°.Examples for tetragonal crystal system is TiO2, SnO2,

#### 3. Orthorhombic crystal system:

In this crystal system, the unit cell edge lengths are different and they are perpendicular to each other. For example a ≠ b ≠ c and α = β = γ = 90.There are four Bravais lattices in this shown below in given figure.They are simple, face centered, body centered and base focused. Examples of orthorhombic crystal systems are BaSO4, K2SO4, SnSO4, etc.

#### 4. Monoclinic crystal system:

In this crystal system, unit cell edge lengths are different. Two unit cell edges are not perpendicular, but they are perpendicular to the third edge. For example, a ≠ b ≠ c; α = γ = 90° ≠ β.This crystal system has only two Bravais lattices shown in given figure . Example of Monoclinic crystal system are CaSO4.2H2O (gypsum), Na3AlF6 (cryolite), etc

#### 5. Triclinic crystal system:

In this glass system, the length of the edge of the unit cell is different and not perpendicular. for example a ≠ b ≠ c and α ≠ β ≠ γ ≠ 90° and all angles are different .Examples for triclinic crystal system are K2Cr2O7, CuSO4. 5H2O, etc

#### 6. Rhombohedral [ Trigonal] crystal system:

In this crystal system, unit cell edges are all lengths equal. The angles between the axes are the same but other than 90°.i.e. a = b = c and α = β = γ ≠ 90°.Examples for Rhombohedral crystal system are As, Bi, Sb, etc

#### 7. Hexagonal crystal system:

In this glass system, two sides of the unit cell edge length are equal and the angle between these edges is 120 °. These two edges are perpendicular to the third edge and are not the same length. Bravais lattice is primitive only

### Biasing of p–n Junction | Forward and Reverse-biased |

Biasing the p-n junction means applying some external voltage to both sides of the p-n junction. Reverse-biased junction and forward-biased junction are two types of biased junction. You should have also good understanding of  N-Type and P-Type Semiconductor before moving towards this topic. Biasing of p–n Junction  Biasing of a p–n junction  means uses of some external voltage across the two sides of the p–n junction. It is divided into two groups  Forward-biased junction :  When the p-side of junction  is connected to the positive terminal of a battery and the n-side of junction is connected to the negative terminal, the p–n junction is said to be a forward-biased junction.  Reverse-biased junction  :If the positive terminal of the battery is connected to the n-side of junction and the negative terminal on the p-side, the p–n junction is said to be a reverse-biased junction. Now we will see about forward and reverse-biased junction in detail.  Related Topic    Bonding in semiconduc

### About N-Type and P-Type Semiconductor | Materials | Example |

Here you will know about  n type and p type semiconductor in details. You can already see about bonding in semiconductor . N type and P type semiconductor is used in electronic appliances.which is the basis of working of all the electronic devices.So lets discuss in this given topic in the details. N type and P Type Semiconductor When some impurities added to the pure semiconductor then it becomes extrinsic semiconductor and this process of adding impurities is known as doping.  Now it depends on the which type of impurities it added to the semiconductor (two types of impurities can be added to semiconductor pentavalent or trivalent). n-type semiconductor : If impurity that is added to the pure semiconductor is a pentavalent ( which has five valance electron ) then it is called n-type semi conductor. p-type semiconductor : If trivalent impurity is added to the semiconductor then it becomes p-type semi conductor. ( Note-List of  n type and p type semiconductor material is given below.

### Engineers Files Explained | Types of file

Today we will learn about engineers files explained, as we know hand tools are used to remove small amounts of material, usually from small areas of the workpiece.   Do you know why hand tools are used ?Hand tools are used because of following reason: If no machine is available,  The workpiece is too large to go on a machine  The shape is too intricate or simply that it would be too expensive to set up a machine to do the work. As you know the necessity of a hand tools now we will know about a hand tool , engineer's files. Engineer’s files Files are used to perform a variety of tasks, from simple removal of sharp edges to producing complex shapes where use of the device is impractical.Files can be obtained in a variety of shapes and in lengths from 150 mm to 350 mm. Single-cut file: When a file has a single series of teeth cut across its face it is called  single-cut file ,Figure of single-cut file is shown below. double-cut file: When a file has double series of teeth cut across